The prevalence of obesity is increasing worldwide and there is a strong consensus that weight gain and obesity are the consequence of a positive energy balance, which occurs when more energy is ingested than expended. Energy intake (food intake) is one of the primary culprits of weight gain, yet few accurate methods exist to measure food intake in people's natural environment or free-living conditions. Consequently, it is difficult for scientists to study food intake, energy balance, weight gain, and obesity. Additionally, it is difficult for people who wish to manage their weight to learn how to modify energy balance, since their ability to manage energy balance is hindered by inaccurate information about energy intake. Food records or food diaries are frequently used to measure energy intake, but they have been found to be inaccurate. When completing a food record, people record the types and amounts of the foods that they eat on pen-and-paper forms. The "gold standard" for measuring energy intake relies on the doubly labeled water method, but this method is costly and not available to most researchers and clinicians. The doubly labeled water method also does not provide information about the types of foods being eaten and the macronutrient composition of the diet. Therefore, this method provides little information about the nutritional adequacy of the diet. Digital photography of foods, a method that has been found to accurately measure energy intake in naturalistic settings (e.g., cafeterias), might also have promise in improving estimates of food intake in free-living individuals. When using this method, the plate of foods selected by an individual is photographed with a digital camera before the meal and plate waste is photographed after the meal. Reference or standard portions of known quantities of the foods are also photographed. In the laboratory, trained judges (registered dietitians) use these photographs to estimate the portion size of food selection and plate waste by comparing these photographs to the photograph of a standard portion. These estimates are entered into a computer application that calculates food intake (food intake = food selection minus plate waste). A series of pilot studies has found that this method can be altered and used in free-living conditions. The purpose of this study is to develop and test innovative technology that will acilitate the collection of accurate energy intake data in free-living humans sing the digital photography method. Participants will take photographs of their food selection and plate waste sing cell phones and these data will be transferred to the researchers'database over the cellular network in ear "real-time." A semi-automated computer application will be developed to automatically identify the foods in these pictures and estimate the amount of food eaten based on he pictures. During the proposed project, this computer application will be developed and the reliability and validity (accuracy) of the method for estimating good intake will be tested in laboratory and free-living conditions. This research promises to significantly advance the study of energy balance and provide a useful tool to clinicians for measuring energy intake.